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South Deep

South Deep Gold Mine is situated in the magisterial districts of Westonaria and Vanderbijlpark (Gauteng province), some 45 kilometres south-west of Johannesburg at latitude 26º 25’ south and longitude 27º 40’ east. It is accessed via the N12 provincial road between Johannesburg and Potchefstroom

Asset fundamentals

Asset fundamentals    
Licence status and holdings   The conversion of the old order mining right to a new order mining right, as required in terms of the Minerals and Petroleum Resources Development Act, No 28, 2002 (the MPRD Act), was approved in July 2010. The aerial extent of the South Deep lease area is 4,268 hectares. All required authorisation has been obtained and is in good standing.
Operational infrastructure and mineral processing  

The workings are accessed from the surface through two shaft systems – the Twin Shaft Complex (main and ventilation shafts to 110 level), of which the main shaft comprises a singledrop to a depth of 2,995 metres, the vent shaft to 2,947 metres and the South Shaft Complex, which is a sub vertical system to 95 level.

The mine has been subdivided into three main areas. ‘Old Mine’ comprises the area above 87 level, and is serviced from the South Shaft Complex. ‘Current Mine’, which is serviced from the Twin and South Shafts, extends from 87 Level to 95 Level. The deeper part of the mine extends from 100 level down to 110 level and comprises the North of Wrench area extending from a depth of 2,700m to 2,900m and the South of Wrench area extending to a final depth of 3,300m.

South Deep Gold Mine operates one gold plant with a design capacity of 330ktpm. The milling circuit consists of a single stage SAG mill for primary followed by secondary milling, utilising two overflow ball mills. Classification is done using cyclone clusters and Knelson concentrators facilitate the recovery of free gold. Free gold is upgraded using a Gemini table and the final concentrate is smelted into bullion.

The cyclone overflow is thickened before the slurry reports to the leach circuit. Cyanide is used for gold dissolution and lime is added to ensure protective alkalinity. An eight-stage, carousel-type CIP circuit is used for gold adsorption. After elution gold is recovered from the solution using electro-winning sludge reactors, dried and gold bullion is produced by smelting in an induction furnace.

Tailings storage facility   The top of the starter wall will be reached by mid-2018 and the end of Phase 1 by mid-2020. The construction of Phase 2 needs to commence in early-2018 and the main penstock needs to be in place by 2029.
Climate   No extreme climate conditions are experienced that may affect mining operations.
Deposit type   Intermediate to deep-level mechanised gold mine (>2,000 m below surface) exploiting auriferous palaeoplacers (reefs), namely the conglomerates that comprise the Upper Elsburg Reefs of the Mondeor Formation. Historically the Ventersdorp Contact Reef (VCR) of the Venterspost Formation has been exploited using conventional mining methods.
Environmental, health and safety   The key issues at South Deep are related to water management. An amendment of the current approved water use licence was submitted in May 2015 and the time period for approval is 300 days. Several key water related projects were commissioned and are being monitored for progress. The mine participates in the Rietspruit Catchment Forum where water related issues are discussed with authorities and other stakeholders and players in the catchment area. The amendment and the consolidation of the current approved environmental management plan (EMP) (2010 and 2012) has commenced, and will be submitted for approval during H1 2016. The mine environmental management system is ISO14001 accredited. Reporting on environmental, sustainable development and community issues is done according to the Global Reporting Initiative requirements. The mine is in full compliance with the ICMC.

Brief history of South Deep

Commercial production of the Western Areas Gold Mine commenced in September 1951. In 1990, Western Areas Gold Mining Company Limited (WAL) shareholders approved the transfer, cession and assignment of certain land and mineral rights to South Deep Exploration Company Limited in exchange for its shares. WAL and South Deep Exploration Company Limited merged on 1 January 1995. Development of 95 Level across to the planned collar position of Twins commenced.

On 1 April 1999, the Placer Dome/Western Areas (PDWA) joint venture (JV) was formed and in February 2000, the name of the mine was changed to South Deep Gold Mine. Sinking of the ventilation shaft was completed to 95 level in 2001 and the main shaft to 110 level in 2002, concurrently a 7,200tpd capacity mill was commissioned. The Twin Shaft Complex was officially opened on 4 February 2005.

Barrick Gold Corporation acquired a majority interest in Placer Dome Inc. on 20 January 2006 and Gold Fields acquired Barrick’s 50% JV interest in the PDWA JV on 1 December 2006. In April 2007, Gold Fields acquired all remaining WAL shares and consequently owned 100% of South Deep Gold Mine at that time.

Post a pre-feasibility study, the ventilation shaft was deepened to 110 level and was commissioned in 2012.

A new-order mining right was granted to South Deep in 2010, including the area known as Uncle Harry’s. During 2011, Newshelf 899 (Proprietary) Limited (Newshelf) was established, which holds a 100% interest in South Deep Gold Mine. Newshelf is a 90% subsidiary of GFI and the remaining 10% is held by outside shareholders as part of the Broad Based Black Economic Empowerment (BBBEE) transaction.

Key developments at South Deep

South Deep is a mine that has been built to extract one of the largest undeveloped gold ore bodies in the world. The ore body encompassing a ~37Moz Mineral Reserve is well understood as a result of a combination of 3D seismic (vibroseis, 2007) modelling, extensive surface drilling (2007-2013) and effective resource modelling that has provided valuable information on the geological structure and gold distribution patterns at the mine. Key required infrastructure is now installed to support the production ramp up and to deliver the mine as a low cost, long life mechanised mining operation. Due to its depth and full mechanisation, South Deep has no real benchmark operation in the industry and the current focus therefore remains on establishing the basic capability at the mine to drive productivity and leverage unit costs. In addition, a strategic review of the operation is being undertaken with the objective of positioning and re-basing South Deep as a core franchise asset, that aims in the first instance to achieve self-funding (breakeven) as early as possible and then to deliver consistent free cash-flow margins going forward.

Setting South Deep up for long-term success

The review by the appointed GRB of South Deep’s current mining layout and methodology was concluded in 2015.

The historic mining corridor and pillar span of 240 metres (corridors) by 60 metres (pillars) has been changed to mining spans initially ranging from 75 metres to a maximum of 180 metres, with pillar widths maintained at 60 metres, with six newly established corridors. This initial variation in mining span will reduce as the new design matures with depth. Instrumentation is being expanded underground to measure rock behaviour in a variety of conditions and to determine the optimal span configuration in the long-term with the aid of numerical modelling. The adopted pillar spacing took into account the position of the Gemsbokfontein dyke and the easterly diverging conglomerate package in a down-dip direction. The configuration will be measured and monitored over the next couple of years as mining progresses further to the south.

The benefits of changing from the historical 240 metre by 60 metre span to the newly designed and modelled pillar design is summarised as follows:

Improved safety
Improved stiffness of regional support design
Will result in less deformation and hence more stable excavations
Increase from 4 to 6 corridors – increase in number of mining attack points (flexibility)
Increased reliability of de-stress operations

The mining methods, which have been under review since 2014, including the 4.5 metre by 4.5 metre de-stress and the Inclined Slot method, have evolved to a high profile de-stress mining method with a mining width of 4.5 metres and a height of 5.0 metres. With the exception of 95 1W and 90 1W de-stress (mature mining areas), the new methodology was rolled-out in all the de-stress mining areas during the latter part of 2015.

The new regional pillar design and the new high profile de-stress mining method have been incorporated into the December 2015 LoM plan. These initiatives, which are supported by the GRB, are aimed at improving safety, increasing mining productivities and simplifying the overall mining cycle.

Additional performance improvement focus areas for 2016 include the following:

Artisan and supervisory mechanised skills development
Implementation of a planned maintenance mining fleet contract in corridor 2
Increased effective face time utilisation
Dilution and ore loss controls
Improved refrigeration water reticulation system
Improved ore handling and backfill placement

 

Plan of the South Deep mining area

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Geographic location
Geographic location

Related links
›  Detailed disclosure of the South Africa Region in the 2015 integrated report